1. Field of the Invention
The present invention relates to an adhesive composition which is particularly suited for using at dicing step where chips are obtained from a semiconductor wafer and a step of die-bonding a chip on an organic substrate or a lead frame and the like, an adhesive sheet having an adhesive layer comprising the above adhesive composition and a production method of a semiconductor device using the above adhesive sheet.
2. Description of the Related Art
A semiconductor wafer of silicon, gallium arsenide or the like is produced in a large size, and this wafer is cut and separated (dicing) into small element pieces (chips) and then transferred to a die-bonding step which is a subsequent step. In this case, the semiconductor wafer is subjected to the respective steps of dicing, washing, drying, expanding and picking-up in the state that it is adhered advance on an adhesive sheet, and then it is transferred to a die-bonding step which is a subsequent step.
In order to simplify the picking-up step and the die-bonding step among the above steps, various adhesive sheets for dicing and die-bonding which are provided with both a wafer-fixing function and a die-adhering function at the same time are proposed (for example, refer to patent documents 1 to 4).
Adhesive sheets comprising a base material and, formed thereon, an adhesive layer comprising a specific composition are disclosed in the patent documents 1 to 4. The above adhesive layer has a function of fixing a wafer in dicing the wafer, and when picking up the chip after finishing dicing, the adhesive layer is peeled off from the base material together with the chip. When the chip provided with the adhesive layer is mounted on a die-pad part of a substrate and heated, an adhesive strength of a thermosetting resin contained in the adhesive layer is revealed to complete adhesion between the chip and the substrate.
Then, a metal wire such as a gold wire is connected to the chip and a wire pad part of the substrate (wire bonding) in order to electrically connect the chip and the wire pad part or a lead part of a metal frame. Subsequently, sealing by transfer molding or potting sealing is conducted for the purpose of providing electrical and physical protection from the external environment. A semiconductor device is completed by mounting solder balls on the back side of the substrate or conducting solder plating on a non-sealed portion of a metal lead frame, so that electrical connection with the external environment is enabled.
The adhesive sheets disclosed in the patent documents described above enables so-called direct die-bonding and makes it possible to omit a step of coating an adhesive for adhering a die. In adhesives disclosed in the above patent documents, a low-molecular-weight energy-beam-curable compound is blended as an energy-beam-curable component. The energy-beam-curable compound is polymerized and cured by irradiating an energy beam before a step of picking up chips that is performed after dicing. As a result, adhesive strength of the adhesive layer decreases and the adhesive layer is easily separated from the base material. Further, after a die bonding where energy-beam curing and heat curing have already been completed, all components in the adhesive layer of the adhesive sheet are cured to strongly bond the chip and the substrate.
The patent document 4 discloses an adhesive composition comprising (A) an adhesive component, (B) a thermosetting adhesive component, and (C) a compound obtained by adding and condensing a silane coupling agent to a polysiloxane oligomer. A compound represented by the following formula is disclosed as the compound (C).

In the above formula, R is a methyl group or an ethyl group, and S is R or a group introduced by the silane coupling agent. Preferably at least two groups introduced by the silane coupling agent are included in one molecule of the compound (C).
In recent years, higher integration of semiconductor devices has been required. In a certain case, plural chips are stacked in a vertical direction within a certain limited height in order to achieving high integration in semiconductor devices. Consequently, it is required that chips constituting the semiconductor devices are further reduced in a thickness.
As the chips become thinner, a peeling strength (a strength necessary to peel an adhesive layer together with a chip from a base material of the adhesive sheet) in picking up chips has increasingly become an important factor which determines a manufacturing yield. If the value of this is high, the chips may be broken or chipped when being picked up, which reduces the manufacturing yield of the chips. The strength of wafers and chips when being conveyed is also a big factor which determines the manufacturing yield.
In summary, the high integration in semiconductor devices that has been recently required decreases the manufacturing yield of the semiconductor devices.
Patent document 1: JP-A-1990-32181
Patent document 2: JP-A-1996-239636
Patent document 3: JP-A-1998-8001
Patent document 4: JP-A-2000-17246